The present invention relates to a device for determining deformations of motor vehicle components.
The release point of a side bag in the case of side impact situations in the motor vehicles is mainly sensed by acceleration sensors. They are mainly located in the region of seat cross members, the sills in the door region, in particular B or C pillars of the vehicle passenger compartment in a motor vehicle.
It has been determined with air pressure sensors that in the case of not side impact-caused pressure increases in the door cavities of the motor vehicles and in the case of exceeding of the sensitive first side bag release threshold, an undesired release of the side bag can occur. This can for example occur in the case of a sudden slam of the vehicle doors or release of the front bags.
In the case of a pole impact in the door center, the shortest side bag release times are required. During the release time the unobjectionable unfolding of a thorax side bag which is built in the vehicle or a side bag which is integrated in the seat back must be guaranteed, so that in this impact situations which can lead to dangerous injuries in the door center a maximum protection at the deformation-critical location is provided for the vehicle occupants. On the other hand, the non-release threshold of a side bag must be set at vehicle speeds between 20 and 25 km/h, to provide the required robustness of the sensor device against an undesirable release in the situations which are not critical for the vehicle occupants, substantially during sudden slams of the vehicle doors.
A very fine parameter adjustment in the release algorithm of the air bag sensors in the cavities of the vehicle doors leads in the case of the danger to desired short release times. On the other hand the release threshold is reduced to undesirable 10-15 km/h vehicle speed, which leads to above described disadvantages.
Pressure sensors in the case of pole impact in the center of a soft vehicle door from the point of view of rigidity have short response times, when compared with acceleration sensors arranged on the vehicle structure, however they have the above mentioned disadvantages. Pressure is a scalar variable, with which it is not important whether they originate from the vehicle interior (pressure build up by simultaneous release of both front air bags by door slams with closed window/sliding roof surfaces) or from outside of the vehicle occupant compartment, for example in the case of a side impact on the vehicle.
Accordingly, it is an object of the present invention to provide a device for determining a deformations of motor vehicle components, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a device for detecting side impacts on a vehicle, wherein on the component of the vehicle, an element is provided which senses a beginning of a plastic component deformation and reduces a release threshold for activation of a side bag.
With the inventive device additionally to the evaluation of signals of peripheral acceleration sensors, the deformation of the door outer plate, for example the plastic door plate deformation is sensed by a strain gauge sensor. The strain gauge sensor is arranged in the cavity between the motor vehicle door exterior and the motor vehicle door interior, for example on a door reinforcing element (tube, profile plate and the like). With the additional detection of the deformation of the door, the door impact can be recognized extremely fast, for example after 3-5 ms.
When additionally to the acceleration sensor, a strain gauge sensor is provided for each vehicle door, the injury-causing side impact situation can be detected after 3-5 ms time interval. With the signal produced by the strain gauge sensor the release threshold of the acceleration sensor provided for example on the B-pillar of a motor vehicle can be reduced, so that the side bag which protects the head and thorax region of the vehicle occupant can be activated in the correct time.
In the case of the use however of a sensor which responds to pressure, a lateral impact can be detected first after approximately 6 ms, with an inflation time of the side bag of approximately 10 ms for the thorax side bag, halving of the detection time means a decisive time benefit with regard to the passive safety of the vehicle occupants.
In addition to the use in the cavity of a vehicle door, the strain gauge sensor in a comparible way can be also mounted in the front body region of a motor vehicle, for example on the front motor hood lower side, for pedestrian impact recognition.
The strain gauge can be riveted in advantageous manner to the deformation bodies whose elastic deformation start is to be sensed, so that any defective components can be easily exchanged, while the component to be monitored, for example a vehicle door can however remain to be used. For this purpose the strain gauge sensor can be riveted simply to the reinforcing bar in the door cavity so that an expensive direct welding or glueing on the deformation part can be dispensed with.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.